• 멤브레인
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• 제25권1호
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• pp.48-59
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• 2015

순수용매와 혼합용매를 사용한 상전이를 통하여 poly(L-lactic acid) (PLLA) 스캐폴드 막을 제조하였다. 순수용매로서 chloroform과 1,4-dioxane을 사용하였으며, 이들 순수용매를 혼합하여 혼합용매를 제조하였다. 스캐폴드 막의 모폴로지, 기계적 특성 그리고, 물질전달 특성을 각각 SEM, 인장강도실험 및 당 확산실험을 통하여 측정, 평가하였다. 순수 chloroform 용매를 사용한 용액으로부터는 격벽-공극 구조(solid-wall pore structure)의 스캐폴드 막이 제조되었다. 반면, 순수 1,4-dioxane 용매를 사용한 용액으로부터는 나노섬유 구조의 스캐폴드 막이 제조되었다. 혼합용매의 경우 용매 내의 조성이 변화하면서 다양한 구조의 스캐폴드 막이 제조되었다. 혼합용매 내 1,4-dioxane 함량이 20% 이하인 경우에는 격벽-공극 구조의 스캐폴드 막이 제조되었으며, 1,4-dioxane 함량이 20%인 경우에는 최대직경 $100{\mu}m$의 거대공극을 갖는 구조를 보였다. 1,4-dioxane 함량이 25% 이상인 구간에서는 나노섬유 구조의 스캐폴드 막이 제조되었다. 이 구간에서는 혼합용매 내 1,4 dioxane 함량이 변화함에 따라 나노섬유의 직경이 함께 변화하였다. 나노섬유의 최소직경은 15 nm 가량이었으며, 혼합용매 내의 1,4-dioxane 함량이 80 wt%일 때에 얻어졌다. 이상의 결과를 통하여 용매의 조성은 스캐폴드 막의 구조를 결정짓는 중요한 요소가 된다는 결론을 얻을 수 있었다.

• 공업화학
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• 제10권3호
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• pp.477-485
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• 1999

방사선 전조사법에 의하여 폴리프로필렌 부직포 상에 2,3-에폭시프로필메타크릴레이트 (GMA)를 공중합시킨 후 다양한 혼합용매 상에서 이미노디아세트산 (IDA)과 반응시킴으로서 고성능의 섬유상 금속 흡착제를 제조하였다. 그라프트 반응시의 그라프트율은 반응시간과 반응온도, 총 조사선량 및 선량율에 의존하는 것으로 나타났다. GMA가 그라프트된 폴리프로필렌 부직포 상에 이미노디아세트산을 도입하는 아민화반응에 있어서 다양한 혼합용매가 반응성에 미치는 영향을 고찰한 결과 디메틸술폭시드 (DMSO)와 물을 적정비율로 혼합한 혼합용매 상에서 가장 높은 반응성을 가지는 것으로 나타났으며, 물만을 사용하는 경우 아민화반응은 전혀 진행되지 않았다. 이온농도 100 ppm으로 조재된 중금속 용액에 제조된 아민화 흡착제를 일정시간 담그어 금속이온에 대한 흡착성능을 살펴보았는데, 각각의 경우에 대하여 흡착효율을 다음의 순서를 따랐다: 납>코발트>철.

• Archives of Pharmacal Research
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• 제28권4호
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• pp.493-501
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• 2005

Effect of solvents on physical characteristics and release characteristics of monolithic acetaminophen (APAP) hydroxypropylmethylcellulose (HPMC) matrix granules and tablets were examined. Various types and amounts of solvents were employed for granulation and coating. APAP and other excipients were mixed and were then wet-granulated in a high-speed mixer. The dried granules were then directly compressed and film-coated with low viscosity grade HPMC. As the amount of water increased, the size of granules also increased, showing more spherical and regular shape. However, manufacturing problems such as capping and lamination in tableting occurred when water was used alone as a granulating solvent. The physical properties of HPMC matrix granules were not affected by the batch size. The initial release rate as well as the amount of APAP dissolved had a tendency to decrease as the water level increased. Addition of nonaqueous solvent like ethanol to water resulted in good physical properties of granules. When compared to water/ethanol as a coating solvent, the release rate of film-coated HPMC matrix tablets was more sensitive to the conditions of coating and drying in methylene chloride/ethanol. Most of all, monolithic HPMC matrix tablet when granulated in ethanol/water showed dual release with about $50\%$ drug release immediately within few minutes followed by extended release. It was evident that the type and amount of solvents (mainly water and ethanol) were very important for wet granulation and film-coating of monolithic HPMC matrix tablet, because the plastic deforming and fragmenting properties of material were changed by the different strengths of the different solvents.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2720-2724
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• 2013

Polynorbornenes prepared by vinyl addition pathway are known to have some desirable characteristics for wider application but they have some critical drawbacks such as brittleness, poor solubility and adhesion. In order to improve these drawbacks, extensive research for the successful homo- and copolymerization of polar functionalized norbornene with olefin has been carried out. Even though considerable advance has been achieved in the polymerization of polar functionalized monomers, successful catalytic systems for the homopolymerization of polar functionalized norbornene are rare. In this study, a novel successful catalytic system for the polymerization of polar functionalized norborene is proposed. This system employs Pd ${\beta}$-diketiminate/borate cocatalyst in water/organic mixed solvents and it is unique due to introduction of water as a component of solvents. Polymers obtained in this study show high Mw with narrow PDI. Effects of several reaction parameters to the polymer activity and properties are investigated and optimal catalytic system are proposed.

• 한국세라믹학회지
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• 제31권3호
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• pp.291-297
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• 1994

Cordierite powders were prepared by controlled hydrolysis of metal alkoxides with catalysts in water medium without using organic solvents. Water was adjusted to a certain pH by HC1 and NH4OH. $\alpha$-Cordierite powder was prepared from aluminum isopropoxide, tetraethyl orthosilicate and magnesium ethoxide mixed with water adjusted to pH of 3. At water pH of 11, $\alpha$-cordierite, mullite and $\beta$-quartz phases were coexisted. The powders were freeze dried, calcined and then fired at different temperatures. The characteristics of powders were examined by means of DTA, X-ray diffraction, FT-IR, and electron microscopy. It was found that $\alpha$-cordierite could be synthesized at temperature of 120$0^{\circ}C$ from the powders prepared by alkoxides with water medium without organic solvents.

• 대한화학회지
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• 제12권3호
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• pp.114-120
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• 1968

Fe-EDTA complex, which is easily formed when Fe salt and EDTA.2Na are mixed in the aqueous medium, is found to be a very effective catalyst in the dehydropolycondensation of aminophenols. In the dehydropolycondensation of aminophenols, the catalyst, Fe(Ⅲ)-EDTA complex (higher oxidation state) is reduced to less stable Fe(Ⅱ)-EDTA complex (lower oxidation state), and the latter is easily oxidized by air to the original higher oxidation state complex, therefore the catalytic action of Fe-EDTA complex is found to be recycled effectively. Under the catalytic action of the above mentioned complex, p-aminophenol is polymerized in the aqueous medium to form the oligomers of p-aminophenol, which the degree of polymerization to be 5 or more. The oligomers formed contain partly quinone nucleus as well as amino and hydroxyl groups. In this study, the effects of the solvents and characteristics of the oligomers are discussed. These types of polymerizations catalyzed by the metallic chelate compounds are considered to be very closely related to the reactions in the living matters.

• 대한안전경영과학회지
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• 제2권2호
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• pp.95-108
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• 2000

Electrochemical charateristics of activated carbon fiber cloth(ACFC) electrode were studied with propylene carbonate(PC), ${\gamma}$-butyrolactone(GBL) and N,N-dimethyl-formamide(DMF) as a solvent and tetraethylammoniumtetrafluoroborate(TEABF$_4$), tetraethylammoniumhexafluorophosphate(TEABF$_{6}$), tetrabutylammoniumtetrafluoroborate(TBABF$_4$) and tetrabutylammonium hexafluorophosphate(TBAPF$_6$) as an electrolytes(active material). The concentrations of electrolytes were in the range of 0.2~1.2 N, the volume ratios of PC and DMF as a mixed solvent system, were 90：10, 80：20, 70：30, 60：40, 50：50, and 40：60 vol%. Electrochemical characteristics such as electric conductivity, internal resistance, and electric capacitance of fabricated unit cells were measured after the moisture of activated material was removed with molecular sieve. Electrochemical characteristics were better in mixed solvents system than in mono solvent system. The mono solvent system of 1.0 N electrolyte of GBL/TEABF$_4$ with activated carbon cloth electrodes showed better result but the mixed solvent system with PC and DMF/TEABF$_4$(50：50 vol%) and the concentration of 1.0 N electrolyte showed the best characteristics. Internal resistance was 3.47 $\Omega$ and specific capacitance was 19.1 F/g respectively.y.

• 멤브레인
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• 제18권4호
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• pp.282-293
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• 2008

친전자성 치환반응으로 제조된 술폰화 단량체, 비(非)술폰화 단량체 및 탄산칼륨을 이용하는 직접 중합법을 통하여 높은 점도의 술폰화 폴리아릴에테르술폰 공중합체를 합성하고, 이들을 원료로 N-메틸-2-피롤리돈(NMP)과 디메틸아세트아미드(DMAc)의 혼합 용매 상에서 직접 메탄을 연료전지용 고분자 전해질 막을 제조하였다. 막 제조 시의 용매 효과에 주목하여 혼합 용매의 부피 비는 $0{\sim}100%$로 변화시키고 공중합체의 술폰화도는 50%로 고정하였다. 이온 전도도 및 메탄올 투과도 측정을 통하여 최종 전해질 막의 기본 특성을 파악하고, 주사전자현미경 및 원자간력현미경분석을 통한 표면 분석 결과와 비교함으로써 이들의 상관관계를 고찰하였다. 막 제조 시의 용매 혼합 비율을 적절히 조절함에 따라 최종 전해질 막의 이온 전도도를 크게 향상시킬 수 있음이 확인되었는데, $25^{\circ}C$의 100% 가습 환경에서 측정된 수소 이온 전도도는 NMP : DMAc 50:50 부피/부피-%에서 최대 $1.38{\times}10^{-1}\;S/cm$이었다.

• 한국안전학회지
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• 제14권3호
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• pp.120-126
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• 1999

This study was accomplished by measuring the lower and upper flash point with air blowing method and grasping the characteristics of flammability for the three component systems, which are made up of the Benzene-Toluene-o-Xylene and Methylethylketone-Toluene-o-Xylene. These three component systems are widely used in the various industrial fields together with the development of industry. The results are as follows ; 1 ) Isothermal line is plotted on the triangular diagram for flash points determined in each solutions. From this line, the mixed compositions which indicated the same lower and upper flash points in each different composition could be read on this diagram, if the composition of mixtures are known. 2) Lower and upper explosion limits obtained from the flash points determined for the three component solution are compared with the value calculated from Le Chatelier's law. Especially the lower explosion limits are in a good agreement with the calculated values.

• 보존과학회지
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• 제34권6호
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• pp.569-580
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• 2018

The possibility of applying poulticing was studied for removing Paraloid B72, a resin used for fixing an earthen mural painting. Five types of poultices were selected from clay and gel types, and acetone, ethanol, and methyl ethyl ketone(MEK) were used as mixed solvents. The possibility of mixing between the poultice and solvent was investigated, and then the spreadability, fluidity, acidity, drying properties, and solubility of the poultices were examined to confirm the characteristics. A poultice agent, which is suitable for applying to a mural painting, was selected and applied to a painting layer sample coated with Paraloid B72. As a result, all painting layers were good condition at under 50% of the solvent. The removal efficiency of Paraloid B72 was more effective when most of the solvents were used at 50%, rather than at 25%. However, it is difficult to mix 50% of MEK and ethanol with the gel-type poultices. When used at 25%, the removal performance was poorer than that at 50%, but the mixing with all the poultices was successful. In addition, the adsorption and removal power of the gel-type poultice were better than those of the clay-type, but the latter was expected to be more suitable in short-time cases due to its high drying speed. The results of this study show that the dissolution performance varies depending on the poultices and solvents. Hence, the poultice and solvent should be selectively applied, considering the fixative of the mural to be removed.